Exception is never thrown in body of corresponding try statement

Question

I have a problem with exception handling in Java  here s my code  I got compiler error when I try to run this line  throw new MojException  Bledne dane     The error is      exception MojException is never thrown in body of corresponding try statement   Here is the code   public class Test     public static void main String   args  throws MojException          TODO Auto-generated method stub      for int i 1 i lt args length i           try          Integer parseInt args i-1                  catch MojException e           throw new MojException  Bledne dane                  try          WierszTrojkataPascala a   new WierszTrojkataPascala Integer parseInt args 0             System out println args i        a wspolczynnik Integer parseInt args i                    catch MojException e           throw new MojException args i      e getMessage                           And here is a code of MojException   public class MojException extends Exception      MojException String s           super s             Can anyone help me with this

User · Accepted Answer

A catch-block in a try statement needs to catch exactly the exception that the code inside the try {}-block can throw (or a super class of that).

try {
    //do something that throws ExceptionA, e.g.
    throw new ExceptionA("I am Exception Alpha!");
}
catch(ExceptionA e) {
    //do something to handle the exception, e.g.
    System.out.println("Message: " + e.getMessage());
}

What you are trying to do is this:

try {
    throw new ExceptionB("I am Exception Bravo!");
}
catch(ExceptionA e) {
    System.out.println("Message: " + e.getMessage());
}

This will lead to an compiler error, because your java knows that you are trying to catch an exception that will NEVER EVER EVER occur. Thus you would get: exception ExceptionA is never thrown in body of corresponding try statement.

User · Answer

Always remember that in case of checked exception you can catch only after throwing the exception either you throw or any inbuilt method used in your code can throw   but in case of unchecked exception You an catch even when you have not thrown that exception

User · Answer

Any class which extends Exception class will be a user defined Checked exception class where as any class which extends RuntimeException will be Unchecked exception class  as mentioned in User defined exception are checked or unchecked exceptions So  not throwing the checked exception be it user-defined or built-in exception  gives compile time error   Checked exception are the exceptions that are checked at compile time   Unchecked exception are the exceptions that are not checked at compiled time

User · Answer

As pointed out in the comments  you cannot catch an exception that s not thrown by the code within your try block  Try changing your code to   try      Integer parseInt args i-1       this only throws a NumberFormatException   catch NumberFormatException e       throw new MojException  Bledne dane        Always check the documentation to see what exceptions are thrown by each method  You may also wish to read up on the subject of checked vs unchecked exceptions before that causes you any confusion in the future

[java] Exception is never thrown in body of corresponding try statement

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